A model for the investigation of factors influencing haemorrhagic necrosis mediated by tumour necrosis factor in tissue sites primed with mycobacterial antigen preparations.

Mycobacterial lesions and skin sites challenged with soluble mycobacterial antigen are very sensitive to the necrotizing effect of tumour necrosis factor (TNF). We have used a model that permits separate quantitative assessment of swelling and haemorrhage to show that when these reactions are elicited in mice that have not been deliberately immunized, pretreatment of the mice with lipopolysaccharide (LPS), or with a MoAb to CR3 which blocks emigration of myeloid cells into the tissues, will block both the swelling and the haemorrhage. On the other hand, treatment with an inhibitor of platelet-activating factor (PAF), or with misoprostol (a synthetic prostaglandin E1 analogue), or with cobra venom factor (CVF) which depletes complement, preferentially blocks the haemorrhagic component, while leaving the swelling relatively unaltered. As swelling occurs before the haemorrhage is seen, it is possible that these factors act at a late stage in the cascade of events leading to the tissue damage. However, LPS and CVF were able to inhibit swelling and haemorrhage in the massive reactions elicited in pre-immunized animals, whereas the PAF inhibitor had no detectable effect.